Promising results for breeding drought-resistant cowpea

Promising results from a crossbred cowpea variety has Texas AgriLife Research scientists hopeful that the drought-resistant trait will soon be available to producers.

Though commonly consumed as a food staple, the cowpea (commonly known as the black-eyed pea) has lots of potential to expand into the feedstock sector in both livestock and cropping systems, according to Dr. B.B. Singh, a visiting professor in the soil and crop sciences department at Texas A&M University.

“Drought is one of the major constraints to agriculture across the world,” Singh said. “The breeders are trying to develop drought-tolerant varieties. Screening for this in the field is very difficult. We’ve brought the drought inside the greenhouse and so far we’ve seen some very favorable results.”

In a greenhouse at Texas A&M in College Station, Singh has been working with a group of scientists to breed a drought-resistant cowpea variety. This type of cowpea could be valuable as a food staple in the U.S., Asia, South America and in Africa where high temperatures and little rainfall dictate growing conditions.

“We’ve been working on this with the goal of understanding the physiology of drought tolerance so we can better breed for it,” said Dave Verbree, a doctoral student in plant breeding and physiology at Texas A&M. “We’re looking at how many genes are involved and breeding drought-tolerant lines that combine only the best traits for a given environment.”

Verbree is using thermal imaging to assist in identifying the superior genotypes that will be used in the crossbreeding experiments, which are done through conventional methods of breeding.

Singh came to the department as a visiting professor following his retirement three years ago from the International Institute of Tropical Agriculture in Africa. He is working with colleagues Creighton Miller, D.C. Sheuring and Dr. Bill Payne, using field trials in College Station as part of research efforts.

The team also is finding solutions to breeding cowpea varieties that are aphid resistant in addition to drought tolerant.

Inside the greenhouse, small boxes with about 4 inches of soil contain test lines that were planted in mid-November.

“Each was watered enough to germinate and grow,” Singh said. “After that, we don’t water them and watch response of each line to drought over time.”

Sixteen varieties were planted on the same day, Singh said. Fifty days later and without any watering, the resistant varieties remained green and fully alive whereas the susceptible ones were completely dead with brown leaves and dried stems.

Promising results

“Our preliminary studies have shown one major gene for drought tolerance,” he said. “We’re trying to transfer that gene into the improved varieties found in Africa, Asia and the U.S. that have good healthful factors and are aphid resistant. We hope these new varieties will have major impact improving food production in southern U.S., Africa, Asia and Brazil.”

The cowpea originated in Africa and was brought to America around 1775. It was used mainly as a fodder crop, and then became a grain crop in the southern U.S. It fixes its own nitrogen, doesn’t need much fertility and is resistant to many diseases. The crude protein in improved varieties can be up to 30 percent.

“We hope in the 21st century when drought, heat and moisture become factors, a 60-day heat- and drought-tolerant cowpea will become the main food legume in the world as it would fit in the existing cereals and root-crops systems as a short-duration niche crop.”

Singh is advocating the cowpea not only as a food crop, but also as crop for livestock that can be cut and baled. Instead of having a grazing cowpea and a food cowpea, Singh envisions having an all-in-one variety from which a producer can get both fodder and food.

Feed grain option

“The U.S. spends a lot of money on feed grain for meat production,” Singh said. “A crop like the cowpea could replace that. This doesn’t need nitrogen, so it needs very little fertilizer, and it doesn’t need much insecticide spray. You get two tons of grain and two tons of fodder per hectare within 60 days.

“The cowpea grains sell for about $500 per ton, so you get enough from grain and feed in protein-rich fodder for cattle. I think this is very exciting for the future, particularly 15 years from now when we have even more drought and water resources become more limited,” Singh said.

The demand for the protein-rich cowpea grains would significantly increase in Asia and Africa with the rise in their population, he added.

Singh has brought to College Station more than 35 lines of cowpeas with drought and aphid tolerance, as well as with resistance to other diseases and higher yield potential. His work there has involved using conventional breeding methods to cross those lines with six Texas and California varieties in greenhouse and field settings.

According to the International Institute of Tropical Agriculture in Africa, the cowpea is an important food crop in many African, Asian and South American countries, especially as an alternative source of protein where people cannot afford meat and fish.

The crop typically is grown by subsistence farmers with limited agricultural resources, who use it to feed livestock or sell for additional income.

Estimates from the International Food and Agriculture Organization and other sources indicate that more than 6 million tons of cowpeas are produced annually worldwide, with sub-Saharan Africa responsible for about 70 percent of that amount. With availability of new short-duration heat- and drought-tolerant and pest-resistant varieties, cowpea production would significantly increase in the coming decades.